JP2003221448A - Aqueous dispersion of polymer and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion of a releasable polymer as fine particles with good storage stability. <P>SOLUTION: The releasable polymer is emulsified in water as a microemulsion having a volume average particle size of 0.1 μm or less by an emulsifier comprising an amphoteric surface active agent to form the aqueous dispersion of a polymer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer water dispersion in which a substance to be dispersed is a microemulsion and a method for producing the polymer water dispersion. INDUSTRIAL APPLICABILITY The polymer aqueous dispersion of the present invention is useful as a water-based release agent, a water-based anti-blocking agent, a water-based slip agent, a water-based water repellent, etc., used for various plastic substrates such as paper substrates, polyvinyl chloride and polyolefins. . In particular, it is useful as a water-based release agent for release sheets, and the release sheet coated with the water-based release agent of the present invention is suitable for protecting and storing the adhesive surface of adhesive tapes, adhesive sheets and the like.

[0002]

2. Description of the Related Art Generally, in the case of pressure sensitive adhesives such as pressure sensitive adhesive tapes and pressure sensitive adhesive sheets, a release sheet is attached to the pressure sensitive adhesive surface or the pressure sensitive adhesive body is wound into a roll to protect the pressure sensitive adhesive surface. The adhesive surface is attached to the back surface of the base material. A release agent is applied to the release surface of the release sheet or the back surface of the base material in order to improve the release property during use.

Conventionally, as the above-mentioned release agent, a silicone-based release agent or a release agent composed of a polymer having a long-chain hydrocarbon group such as a long-chain alkyl group (hereinafter referred to as a long-chain alkyl-based release agent) has been used. However, since long-chain alkyl-based release agents are superior in re-adhesiveness, writability and printability as compared with silicone-based release agents, long-chain alkyl-based release agents have recently attracted attention. For example, Japanese Patent Publication 60-303
Japanese Patent Publication No. 55 proposes to use a polymer obtained by reacting ethylene vinyl alcohol with an alkyl isocyanate as a solvent-type release agent.

Further, a technique for making a long-chain alkyl-based stripping agent water-based has been proposed in consideration of working environment and pollution. For example, Japanese Patent Laid-Open No. 61-113678 discloses that
The long-chain alkyl-based peeling agent is obtained by reacting the raw materials under stirring in water. Further, in JP-A-9-111197 and JP-A-9-29756, an aqueous dispersion obtained by emulsifying and dispersing a release polymer having a long-chain alkyl group in water is used as an aqueous release agent.

A water-based release agent comprising an aqueous dispersion of a release polymer having a long-chain alkyl group is a water-based dispersion obtained so that the coating material is a thin layer generally considered to be useful. The volume average particle diameter of the emulsion in the body is fine, and it is required to be an aqueous dispersion having good storage stability and dispersion stabilization. The volume average particle diameter of the dispersed substance of the water dispersion is generally about 0.1 to several μm.

However, the volume average particle diameter of the dispersed substance is 0.1.
When an aqueous dispersion having a particle size of about several μm is applied as a release agent to various substrates, the thickness of the release layer of the release sheet obtained is generally 0.1 μm or more, and the surface shape also has large irregularities. Moreover, the emulsifier used is unevenly distributed on the particle interface of the emulsion, and uniform peelable film characteristics cannot be obtained.

Therefore, these release-treated surfaces are coated with a large amount of release agent, resulting in poor surface smoothness and nonuniform composition. Therefore, when the release sheet is applied to the pressure-sensitive adhesive tape, the release property of the peelable polymer or the emulsifier into the pressure-sensitive adhesive causes the deterioration of the pressure-sensitive adhesive property. It is also not economically useful.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an aqueous dispersion of a releasable polymer in which a releasable polymer as a substance to be dispersed is dispersed in water as fine particles with good storage stability, and a method for producing the same. To aim. Furthermore, it is an object of the present invention to provide an aqueous release agent comprising an aqueous dispersion of the releasable polymer, which does not affect the adhesive property of the adhesive such as an adhesive.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by an aqueous dispersion of a peelable polymer shown below, and the present invention is solved. Came to do.

That is, the present invention is characterized in that a dispersoid containing a releasing polymer is emulsified and dispersed in water as a microemulsion having a volume average particle diameter of 0.1 μm or less by an emulsifier containing an amphoteric surfactant. And a polymer water dispersion.

The substance to be dispersed in the polymer aqueous dispersion of the present invention is a microemulsion of ultrafine particles.
Moreover, by using the amphoteric surfactant as the emulsifier, the substance to be dispersed can be emulsified and dispersed in the state of ultrafine particles with good storage stability. With an emulsifier other than an amphoteric surfactant, it is difficult to obtain a microemulsion of ultrafine particles, and a release-treated product having an appropriate thickness may not be obtained even when used as an aqueous release agent. The volume average particle diameter is preferably 0.1 μm or less. Furthermore, the volume average particle size is
It is preferably 0.005 to 0.08 μm. The polymer aqueous dispersion of the present invention has good storage stability even when the particles to be dispersed are ultrafine particles having such a very small volume average particle diameter. It also has excellent transparency.

The above polymer aqueous dispersion is particularly suitable when the peelable polymer is a peelable polymer having a long-chain alkyl group having 8 or more carbon atoms.

In the aqueous polymer dispersion, the emulsifier is preferably a combination system of an amphoteric surfactant and a nonionic surfactant.

When the emulsifier is used in combination, the volume average particle diameter of the substance to be dispersed in the obtained water dispersion is reduced, and the storage stability of the water dispersion is improved.

The present invention also relates to an aqueous release agent containing the above-mentioned aqueous polymer dispersion. Although the polymer aqueous dispersion of the present invention can be used in various applications, it is particularly useful as an aqueous release agent, and provides a thin layer coating which does not cause a problem such as contamination on the adhesive surface of the adhesive. You can
In the preparation of the water-based stripping agent, various additives can be added according to a conventional method.

The present invention is also characterized in that a dispersoid containing a releasable polymer, an emulsifier containing an amphoteric surfactant, and a mixture containing water are dissolved by heating under stirring and then cooled. A method for producing an aqueous dispersion.

The method for producing a polymer aqueous dispersion in which the substance to be dispersed is a microemulsion is not particularly limited as long as the polymer aqueous dispersion can be obtained.
The above manufacturing method can be adopted. The dispersoid containing the releasable polymer and the aqueous dispersion medium containing the amphoteric surfactant are heated to a high temperature to uniformly dissolve the system, and then cooled to room temperature, whereby the releasable polymer which is the object to be dispersed. Can be emulsified and dispersed in water as a microemulsion of ultrafine particles with good storage stability. In this way, since the peelable polymer is precipitated from the system in a dissolved state, the diameter of the particles of the dispersed substance to be purified can be reduced, and the volume average particle diameter is 0.1 μm.
It is possible to produce a polymer aqueous dispersion of a microemulsion of m or less. In the above-mentioned production method, even if an emulsifier other than the amphoteric surfactant is used, the releasable polymer is unlikely to be in a dissolved state, and it is difficult to obtain a microemulsion of ultrafine particles.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A peelable polymer having a long-chain alkyl group having 8 or more carbon atoms is preferably used as a peelable polymer which is a substance to be dispersed in a polymer aqueous dispersion of the present invention. When the carbon number is 7 or less, there is a problem in peelability.
Examples of the long-chain alkyl group having 8 or more carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group,
Hexadecyl group, octadecyl group, eicosyl group and the like can be mentioned, and the long-chain alkyl group usually has about 8 to 22 carbon atoms. The carbon number is preferably 12 to 20 from the viewpoint of polymer releasability.

As the peelable polymer, for example, a copolymer of the above-mentioned alkyl acrylate and / or methacrylic acid alkyl ester having a long-chain alkyl group and a polar group monomer such as acrylic acid, methacrylic acid or acronitrile is used. can give. Other monomers may be further copolymerized with these copolymers as long as the releasability of the polymer is not impaired.

Further, as the peelable polymer other than the above, a polymer having an active hydrogen group and a functional group capable of reacting with an active hydrogen such as an isocyanate group, a carboxylic acid group, an acid halide, a ketene group, an aldehyde group and an epoxy group. A modified polymer modified with a long-chain alkyl compound having at least one group and having an alkyl group having 8 or more carbon atoms can be used. Examples of the polymer having active hydrogen include partially saponified polyvinyl acetate, polyvinyl alcohol, ethylene-vinyl alcohol, butyral resin, polyethyleneimine, cellulose resin, methacrylic acid methyl ester-acrylic acid copolymer, and the like. Examples of the long-chain alkyl compound having a functional group include octadecyl isocyanate, docosanyl isocyanate, octadecanoic acid, docosanoic acid, octadecanoyl fluoride, docosanoyl chloride and the like.

The proportion of the long-chain alkyl group in the peelable polymer is not particularly limited as long as the polymer has peelability, but the proportion of the long-chain alkyl group is 50-9.
It is preferably about 0% by weight.

The weight average molecular weight of the peelable polymer is
It is preferably about 10,000 to 500,000. Particularly, those of 50,000 to 400,000 are preferable. If it is less than 10,000, the ability to form a releasable film tends to be poor, and if it exceeds 500,000, the solubility of the polymer may be deteriorated, causing a problem in workability.

An amphoteric surfactant is used as the emulsifier used for forming the aqueous dispersion of the present invention. As the amphoteric surfactant, both an amino acid type amphoteric surfactant and a betaine type amphoteric surfactant can be used. Examples of the amphoteric surfactant include betayl lauryldimethylaminoacetate, betaine stearylmethylaminoacetate, lauryldimethylamine oxide, 2-alkyl-
N-carboxymethyl-N-hydroxyethyl imidazolium betaine, lauric acid amidopropyl betaine,
Examples include amide propyl propyl betaine, lauryl hydroxysulfobetaine, and the like.

The emulsifier may contain a nonionic surfactant in addition to the amphoteric surfactant. As the nonionic surfactant, for example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, sorbitan monostearate,
Examples thereof include sorbitan monooleate and polyethylene glycol monostearate.

When a nonionic surfactant is used as the emulsifier, the amphoteric surfactant: nonionic surfactant (weight ratio) is preferably adjusted to about 1: 1 or less. In order to efficiently obtain a microemulsion, the above ratio should be about 1: 1 to 0.1-1, more preferably 0.5: 1.
It is preferably adjusted to 0.2: 1.

In the production of the polymer aqueous dispersion of the present invention, first, the mixture containing the releasable polymer, the emulsifier containing the amphoteric surfactant, and water is heated to uniformly dissolve the mixture. . The mixture is heated until the temperature in the system reaches 80 to 95 ° C. Warming is performed with gentle stirring. The stirring condition is not particularly limited, but it is usually performed with a propeller blade at about 100 rpm. Then the mixture is gradually cooled to room temperature. A cooling means can be adopted for cooling, but it may be carried out by leaving it at room temperature.

In the method for producing the polymer aqueous dispersion, 100 parts by weight (dry weight) of the releasable polymer is used.
The emulsifier (dry weight) is preferably blended in a proportion of 200 parts by weight or less. The amount of the emulsifier used is preferably as small as possible from the characteristics of the release agent, and the emulsifier does not migrate to the pressure-sensitive adhesive in contact with the release-treated surface or reduce the adhesive strength of the pressure-sensitive adhesive and prevent the contamination of the pressure-sensitive adhesive. The cause disappears. The amount of the emulsifier used is more preferably 100 parts by weight or less. On the other hand, in order to obtain an aqueous dispersion having good storage stability, the amount of the emulsifier used is preferably 20 parts by weight or more, more preferably 0.5 parts by weight or more.

The peelable polymer is previously dissolved in an organic solvent such as benzene, toluene or ethyl acetate,
It is preferably prepared by mixing with the emulsifier and water.

The production apparatus used for producing the polymer aqueous dispersion is equipped with a stirring blade capable of uniformly mixing the system,
Any container having a heating and cooling function may be used. As described above, an aqueous dispersion having a microemulsion as a substance to be dispersed can be obtained with a container having a very simple structure.

The microemulsion obtained by emulsification and dispersion can be made into a desired aqueous dispersion by removing the organic solvent by pressure reduction-heat treatment or the like. The dry weight concentration of the obtained aqueous dispersion is not particularly limited, but is usually 0.5 to 70.
It is preferably about wt%, more preferably 1 to 60 wt%.

[0031]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 Copolymer of octadecyl methacrylate and acrylic acid (molar ratio: octadecyl methacrylate / acrylic acid =
85/15, weight average molecular weight 50,000) was dissolved in toluene to give a 25% solution. The copolymer was prepared by an ordinary radical solution polymerization method. 100 g of the obtained peelable polymer solution, an emulsifier (6.25 g of amidopropyl betaine laurate as an amphoteric surfactant and 18.8 g of polyoxyethylene cetyl ether as a nonionic surfactant) and 3500 g of distilled water were heated to provide a cooling function. It was placed in a container equipped with a stirring blade. Then, the mixture was gently heated to 95 ° C. with stirring. Then, it was cooled to room temperature with gentle stirring. Then, the solvent was removed to obtain a semitransparent water dispersion of the peelable polymer. The dry weight concentration of the aqueous dispersion of the peelable polymer was 1.4%.

Example 2 As a release polymer, a reaction product of a partially saponified product of polyvinyl acetate (saponification degree: 88%, weight-average molecular weight: 90,000) with octadecyl isocyanurate was used. In Example 1, 100 g of a 20% toluene solution of the reaction product was used as a peelable polymer solution, and an amphoteric surfactant, lauryl dimethylaminoacetic acid betaine 1 was used as an emulsifier.
The same treatment as in Example 1 was carried out except that 0 g and 1750 g of distilled water were used to obtain a translucent water dispersion of a peelable polymer. The dry weight concentration of the aqueous dispersion of the peelable polymer was 1.2%.

Comparative Example 1 A formulation was prepared in which the peelable polymer solution, emulsifier (amphoteric surfactant and nonionic surfactant) and water used in Example 1 were mixed in the same amounts as in Example 1. This compound was used as an emulsifying machine in T.K. K homoluxer MARKII (manufactured by Tokushu Kika Kogyo Co., Ltd.) was emulsified and dispersed at a rotation speed of 8000 rpm for 5 minutes to obtain an aqueous dispersion of a peelable polymer.

Comparative Example 2 In Example 1, 5 g of stearyltrimethylammonium chloride, which is a cationic surfactant, and 2.5 g of polyethylene glycol monostearate (HLB: 19.4), a nonionic emulsifier, were used as emulsifiers and distilled. An aqueous dispersion of a peelable polymer was obtained in the same manner as in Example 1 except that the amount of water used was changed to 192.5 g.

The aqueous dispersions of the peelable polymer obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[Volume Average Particle Diameter] A volume average particle diameter (μ) of the substance to be dispersed in the aqueous dispersion obtained by performing laser diffraction (scattering method) with a viscosity distribution measuring device (Horiba Ltd.).
m) was calculated.

[Storage Stability] The aqueous dispersion (200 g) was stored in a glass container with a lid at room temperature for 3 weeks and then visually observed. The case where no sedimentation or separation was observed was regarded as good, and the case where sedimentation or separation was observed was regarded as poor.

[Film Contamination] A water dispersion having a thickness of 38 μm
A polyester sheet having a thickness of 0.5 μm was coated on the polyester film to prepare a release sheet having a release film. The transparency of this film is AU manufactured by Nippon Denshoku Industries Co., Ltd.
TOMATIC DIGITAL HAZEMETER
The haze value was measured with. The smaller the haze value, the better. The haze value of a polyester film having a thickness of 38 μm is 6.5.

[0040]

[Table 1] From Table 1, it is recognized that the water dispersions of the examples are microemulsions in which the volume average particle diameter of the material to be dispersed is ultrafine particles, the storage stability is good, and the transparency of the film is good.

Claims (5)

[Claims] 1. A polymer characterized in that a dispersoid containing a releasable polymer is emulsified and dispersed in water as a microemulsion having a volume average particle diameter of 0.1 μm or less by an emulsifier containing an amphoteric surfactant. Water dispersion. 2. The polymer water dispersion according to claim 1, wherein the peelable polymer is a peelable polymer having a long-chain alkyl group having 8 or more carbon atoms. 3. The polymer aqueous dispersion according to claim 1, wherein the emulsifier is a combination system of an amphoteric surfactant and a nonionic surfactant. 4. A water-based stripping agent containing the polymer water dispersion according to claim 1. 5. A dispersoid containing a peelable polymer, an emulsifier containing an amphoteric surfactant, and a mixture containing water are heated and dissolved under stirring, and then cooled.
4. The method for producing the polymer aqueous dispersion according to any one of 3 to 3.